
/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef struct
{
    ngx_str_t before_body;
    ngx_str_t after_body;

    ngx_hash_t   types;
    ngx_array_t *types_keys;
} ngx_http_addition_conf_t;


typedef struct
{
    ngx_uint_t before_body_sent;
} ngx_http_addition_ctx_t;


static void     *ngx_http_addition_create_conf(ngx_conf_t *cf);
static char     *ngx_http_addition_merge_conf(ngx_conf_t *cf, void *parent,
                                              void *child);
static ngx_int_t ngx_http_addition_filter_init(ngx_conf_t *cf);


static ngx_command_t ngx_http_addition_commands[] = {

    {ngx_string("add_before_body"),
     NGX_HTTP_MAIN_CONF | NGX_HTTP_SRV_CONF | NGX_HTTP_LOC_CONF
         | NGX_CONF_TAKE1,
     ngx_conf_set_str_slot, NGX_HTTP_LOC_CONF_OFFSET,
     offsetof(ngx_http_addition_conf_t, before_body), NULL},

    {ngx_string("add_after_body"),
     NGX_HTTP_MAIN_CONF | NGX_HTTP_SRV_CONF | NGX_HTTP_LOC_CONF
         | NGX_CONF_TAKE1,
     ngx_conf_set_str_slot, NGX_HTTP_LOC_CONF_OFFSET,
     offsetof(ngx_http_addition_conf_t, after_body), NULL},

    {ngx_string("addition_types"),
     NGX_HTTP_MAIN_CONF | NGX_HTTP_SRV_CONF | NGX_HTTP_LOC_CONF
         | NGX_CONF_1MORE,
     ngx_http_types_slot, NGX_HTTP_LOC_CONF_OFFSET,
     offsetof(ngx_http_addition_conf_t, types_keys),
     &ngx_http_html_default_types[0]},

    ngx_null_command};


static ngx_http_module_t ngx_http_addition_filter_module_ctx = {
    NULL,                          /* preconfiguration */
    ngx_http_addition_filter_init, /* postconfiguration */

    NULL, /* create main configuration */
    NULL, /* init main configuration */

    NULL, /* create server configuration */
    NULL, /* merge server configuration */

    ngx_http_addition_create_conf, /* create location configuration */
    ngx_http_addition_merge_conf   /* merge location configuration */
};


ngx_module_t ngx_http_addition_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_addition_filter_module_ctx, /* module context */
    ngx_http_addition_commands,           /* module directives */
    NGX_HTTP_MODULE,                      /* module type */
    NULL,                                 /* init master */
    NULL,                                 /* init module */
    NULL,                                 /* init process */
    NULL,                                 /* init thread */
    NULL,                                 /* exit thread */
    NULL,                                 /* exit process */
    NULL,                                 /* exit master */
    NGX_MODULE_V1_PADDING};


static ngx_http_output_header_filter_pt ngx_http_next_header_filter;
static ngx_http_output_body_filter_pt   ngx_http_next_body_filter;


static ngx_int_t
ngx_http_addition_header_filter(ngx_http_request_t *r)
{
    ngx_http_addition_ctx_t  *ctx;
    ngx_http_addition_conf_t *conf;

    if (r->headers_out.status != NGX_HTTP_OK || r != r->main)
    {
        return ngx_http_next_header_filter(r);
    }

    conf = ngx_http_get_module_loc_conf(r, ngx_http_addition_filter_module);

    if (conf->before_body.len == 0 && conf->after_body.len == 0)
    {
        return ngx_http_next_header_filter(r);
    }

    if (ngx_http_test_content_type(r, &conf->types) == NULL)
    {
        return ngx_http_next_header_filter(r);
    }

    ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_addition_ctx_t));
    if (ctx == NULL)
    {
        return NGX_ERROR;
    }

    ngx_http_set_ctx(r, ctx, ngx_http_addition_filter_module);

    ngx_http_clear_content_length(r);
    ngx_http_clear_accept_ranges(r);
    ngx_http_weak_etag(r);

    r->preserve_body = 1;

    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_addition_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    ngx_int_t                 rc;
    ngx_uint_t                last;
    ngx_chain_t              *cl;
    ngx_http_request_t       *sr;
    ngx_http_addition_ctx_t  *ctx;
    ngx_http_addition_conf_t *conf;

    if (in == NULL || r->header_only)
    {
        return ngx_http_next_body_filter(r, in);
    }

    ctx = ngx_http_get_module_ctx(r, ngx_http_addition_filter_module);

    if (ctx == NULL)
    {
        return ngx_http_next_body_filter(r, in);
    }

    conf = ngx_http_get_module_loc_conf(r, ngx_http_addition_filter_module);

    if (!ctx->before_body_sent)
    {
        ctx->before_body_sent = 1;

        if (conf->before_body.len)
        {
            if (ngx_http_subrequest(r, &conf->before_body, NULL, &sr, NULL, 0)
                != NGX_OK)
            {
                return NGX_ERROR;
            }
        }
    }

    if (conf->after_body.len == 0)
    {
        ngx_http_set_ctx(r, NULL, ngx_http_addition_filter_module);
        return ngx_http_next_body_filter(r, in);
    }

    last = 0;

    for (cl = in; cl; cl = cl->next)
    {
        if (cl->buf->last_buf)
        {
            cl->buf->last_buf      = 0;
            cl->buf->last_in_chain = 1;
            cl->buf->sync          = 1;
            last                   = 1;
        }
    }

    rc = ngx_http_next_body_filter(r, in);

    if (rc == NGX_ERROR || !last || conf->after_body.len == 0)
    {
        return rc;
    }

    if (ngx_http_subrequest(r, &conf->after_body, NULL, &sr, NULL, 0) != NGX_OK)
    {
        return NGX_ERROR;
    }

    ngx_http_set_ctx(r, NULL, ngx_http_addition_filter_module);

    return ngx_http_send_special(r, NGX_HTTP_LAST);
}


static ngx_int_t
ngx_http_addition_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter  = ngx_http_addition_header_filter;

    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter  = ngx_http_addition_body_filter;

    return NGX_OK;
}


static void *
ngx_http_addition_create_conf(ngx_conf_t *cf)
{
    ngx_http_addition_conf_t *conf;

    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_addition_conf_t));
    if (conf == NULL)
    {
        return NULL;
    }

    /*
     * set by ngx_pcalloc():
     *
     *     conf->before_body = { 0, NULL };
     *     conf->after_body = { 0, NULL };
     *     conf->types = { NULL };
     *     conf->types_keys = NULL;
     */

    return conf;
}


static char *
ngx_http_addition_merge_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_http_addition_conf_t *prev = parent;
    ngx_http_addition_conf_t *conf = child;

    ngx_conf_merge_str_value(conf->before_body, prev->before_body, "");
    ngx_conf_merge_str_value(conf->after_body, prev->after_body, "");

    if (ngx_http_merge_types(cf, &conf->types_keys, &conf->types,
                             &prev->types_keys, &prev->types,
                             ngx_http_html_default_types)
        != NGX_OK)
    {
        return NGX_CONF_ERROR;
    }

    return NGX_CONF_OK;
}
